Servicing of refrigeration systems. Substitution of R502 for R402A, R408A, R402B

• Substitution of R12 for R134a
• Substitution of R502 for R404A or R507
• Substitution of R12 for R401A, R409A, R401B. Substitution of R500 for R401B.
• Substitution of R502 for R402A, R408A, R402B
• Substitution of R22 for R407C

Methods of substituting of R502 refrigerant for R402A, R408A, R402B are analogous to the methods of substitution of R12 for R401A, R409A, R401B. Below there is given the list of operations on substitution of R502 refrigerant for R402A, R408A, R402B:

• Determination of working parameters of the operating refrigeration system during operation on R502;
• Removal of R502 out of the system and its utilization. For removal of the refrigerant it is necessary to create 30...35 кPа vacuum. For utilization it is necessary to use the ballon (one cannot let the refrigerant into the atmosphere);
• Drainage of the oil out of the compressor (if only alkylbenzene oils are not used in the compressor) and measuring of its quantity;
• Filling of the refrigeration system with alkylbenzene or polyester lubricating oil. Quantity of the oil being charged into the system should be equal to quantity of the drained off oil;
• Repeated assembling of the compressor (if it has been disassembled);
• Substitution of the filter-dehydrator for the new one which is allowed for dehydrating of R402A, R408A and R402B refrigerants. There are use two types of filters-dehydrators: the one with the inner package containing adsorbent; the one with bulk extender-adsorbent HN-9, MS-594 or the ones equivalent to them;
• Vacuumization of the refrigeration system. Exhaustion with vacuum pump should be performed till 66,5 Pа;
• Checking of hermiticity of the refrigeration system (after checking the system should be exhausted once again);
• Charging of the system with the refrigerant. Charging is realized with the refrigerant in the liquid phase; liquid should be poured out only from the ballon. First 75...80 % is charged (after mass) of the initial quantity of R502. Mass of the charged refrigerant is put down;
• Start of the refrigeration system and its topping-up in order to obtain required working parameters. During toping-up, the liquid is poured out only from the ballon. If the charged portion is small, then the liquid refrigerant should be added by 2...3 % of the initial mass of R502. Mass of the charged refrigerant is put down. Complete mass of the charged refrigerant is obtained by adding previous results;
• Marking of the refrigeration system with labels indicating the type of the refrigerant and lubricating oil (alkylbenzene or polyester).

During the start, for estimation of operation of the refrigeration system they use the following tables.

Expected changing of operational parameters of the refrigeration system after substitution of R502 for R402A, R402B, R408A is given in the table.

Experience of operation with R401A, R409A and R401B shows that in the systems charged with one of these refrigerants, there can be successfully used mineral oil in those cases when oil return from the evaporator into the compressor is not vitally important. To such systems there are referred, for example, chamber refrigerators, refrigeration windows, commercial refrigeration automatic machines and domestic refrigerators. However, in the systems with poor oil return, substitution of mineral oil for synthetic oil can occur necessary, especially if the evaporator is remote from the compressor or is situated lower than the compressor or there are areas in the system with low speed of the refrigerant movement.